Issue webhook does not include milestone detail or milestone group ID

Webhooks that are returned for issue adds/updates include a milestone ID, but no details on the milestone itself. This necessitates another hit to the API to query the milestone, which is fine for project milestones, but is impossible for group milestones as the group ID is not present in the webhook JSON. In addition, there isn't even an indication in the JSON as to whether the milestone is a project milestone or a group milestone.

Current workaround is to re-query the API for the entire issue, which does contain the milestone details; this is a less elegant and more expensive API call.

Propose including the milestone details in the JSON returned by the issue webhook, or at the very least an indication of the group ID for the group milestone.